Thinking, Fast and Slow - Daniel Kahneman

answer have missed an obvious social cue; they should have wondered why anyone would
include in a questionnaire a puzzle with such an obvious answer. A failure to check is
remarkable because the cost of checking is so low: a few seconds of mental work (the problem
is moderately difficult), with slightly tensed muscles and dilated pupils, could avoid an
embarrassing mistake. People who say 10¢ appear to be ardent followers of the law of least
effort. People who avoid that answer appear to have more active minds.
Many thousands of university students have answered the bat-and-ball puzzle, and the
results are shocking. More than 50% of students at Harvard, MIT, and Princeton ton gave the
intuitive—incorrect—answer. At less selective universities, the rate of demonstrable failure to
check was in excess of 80%. The bat-and-ball problem is our first encounter with an
observation that will be a recurrent theme of this book: many people are overconfident, prone
to place too much faith in their intuitions. They apparently find cognitive effort at least mildly
unpleasant and avoid it as much as possible.
Now I will show you a logical argument—two premises and a conclusion. Try to determine,
as quickly as you can, if the argument is logically valid. Does the conclusion follow from the
premises?
All roses are flowers.
Some flowers fade quickly.
Therefore some roses fade quickly.
A large majority of college students endorse this syllogism as valid. In fact the argument is
flawed, because it is possible that there are no roses among the flowers that fade quickly. Just
as in the bat-and-ball problem, a plausible answer comes to mind immediately. Overriding it
requires hard work—the insistent idea that “it’s true, it’s true!” makes it difficult to check the
logic, and most people do not take the trouble to think through the problem.
This experiment has discouraging implications for reasoning in everyday life. It suggests
that when people believe a conclusion is true, they are also very likely to believe arguments
that appear to support it, even when these arguments are unsound. If System 1 is involved, the
conclusion comes first and the arguments follow.
Next, consider the following question and answer it quickly before reading on:
How many murders occur in the state of Michigan in one year?
The question, which was also devised by Shane Frederick, is again a challenge to System 2.
The “trick” is whether the respondent will remember that Detroit, a high-crime c thigh-